Reflecting electric lamp



Jan. l7, 1939. Y c. B lRDsEYE 2,144,044

I REFLECTING ELECTRIC LAMP Fild Nov. 8, 1955 2 Sheets-Sheet 1 Jan. 17, 1939.

C. BIRDSEYE REFLEQT ING ELECTRI C LAMP File d Nov. 8. 1935 ----Lumer2s Sheets-sheaf 2 wwb mga Patented 17, 1939 UNITED STATES 2,144,044 memo ELECTRIC LAMP Clarence Birdseye, Gloucester, Mass, assignor to Birdseye Electric Company, Gloucester, Mesa, a corporation of Delaware Application November 8, 1935, Serial No. 48,853

6Claims.

This invention relates to electric lamps and consists in a reflecting lamp adapted for use in illuminating with high efficiency definite predetermined surfaces which may be of irregular area 5 or unsymmetrical contour.

Important fields of use of my invention are in illuminating show windows, parking spaces, billboards and the like where it is desired to light brilliantly certain sharply defined areas without in wasting any of the lamp rays out of the lighted area. Heretofore attempt has been made to meet such requirements by the use of special reflectors surrounding the lamp and designed to direct its rays into the desired field. A serious objection to iii this expedient is that it is practically impossible to keep such reflectors clean and that their elliciency is greatly impaired by even a light coating of surface dust. Moreover, external reflectors require considerable space which is not always avail- 2 able and in their use there is an inevitable waste of light in those rays which must pass once or twice through the glass of the lamp bulb in reaching or leaving the reflector.

I have discovered that these objections may be 25 obviated and other important advantages secured by employing a bulb of asymmetrical shape provided upon either inside or outside walls with a reflecting metallic coating such as silver. The bulb may be given practically any desired shape 30 in accordance with the requirements of its use, that is to say, its walls may be of unequal length or disposed at unequal angles of divergence, or, in general, depart in any desired plan from bulbs heretofore used and having walls which are sur- 35 faces .of revolution concentric with respect to the longitudinal axis of the bulb. It is believed that heretofore no lamps having asymmetrical bulbs with an applied reflecting coating have been available to the public and the present invention 49 aims to supply such deficiency and provide a compact and eflicient unit for lighting areas of the character discussed.

While for many reasons I prefer to apply the reflecting coating to the inside surface of the bulb, 45 the invention is not limited in this respect but contemplates also the employment of a. metallic reflecting surface applied to the outside walls of the bulb.

For purposes of illustration I will now describe my my invention as embodied in an electric lamp adapted for illuminating the rectangular space behind a show window and a portion of the wall bounding the display space. The features of the invention will be best understood and appreciated from a description of this illustrative embodiment in connection with the accompanying drawings, in which,-

Fig. 1 is a plan view of the lamp,

Fig. 2 is a view in cross section on the line 2-2 of Fig. 1,

Fig. 3 is a. view in side elevation,

Fig. 4 is a view in end elevation,

Fig. 5 is a view in elevation showing the lamp in position in a show window space,

Fig. 6 is a similar view in end elevation,

Fig. '7 is a plan view of the same,

Fig. 8 is aview of the lamp of Fig. 1 in cross section on the plane 88 of Fig. 2,

Fig. 9 is a polar intensity diagram showing the. luminous intensity of light from the lamp in planes A, B and C which are perpendicular to the floor of the window as shown in Fig. "l, and

Fig. 10 is a diagrammatic view showing the luminous intensity of the lamp along the lines D,

E, and F of Fig. '7.

In the bulbs of my invention I do not depend on the element of chance, nor content myself with merely blocking with the silver coating certain areas so as to control in an ineflicient and makeshift manner and with little accuracy, the pattern of the light falling within the desired area. Moreover, by such means only the pattern area and not the intensity distribution and gradient is controlled. In the bulbs of my invention I design and shape the actual glass surfaces of the bulb, so that when the metallic highly eillcient reflecting coating has been applied to these parts they act so as to direct the reflected light positively in the several directions desired, and with the result that within limits, almost any desired pattern of the illuminated area and almost any desired intensity gradient over this area may be positively obtained. i

For example, in a lamp designed and shaped and silvered for lighting a corner show window space in a store with windows on two sides, the light to be overhead and at the outer corner of the windows, I have found it possible tau manufacture a commercial bulb, which when so situated will illuminate with substantially uniform intensity the entire rectangular floor area of the show window space, and with very little of the useful light falling elsewhere than on this useful area. Slightly different shapes have been made for lighting bill-boards in this manner. Foot lights 5 for use on stage, etc'., etc. all require modifications of the actual shapes of the walls of the bulbs, and therefore of the reflecting surfaces to suit the particular requirements of a given type of work, and in all cases this can be accomplished by propf erly designing the bulb and its partial metallic reflecting surface, and so obtain the result at a very low cost, with an extremely high degree of efllciency, which remains constant over the whole life of the bulb.

The bulb herein shown may be given the desired shape by blowing it into a properly designed mold or in some cases a symmetrical bulb may be remolded to shape. The bulb shown in Figs. 1-4 and 8 includes a neck, metallic base and filament mount of conventional character. In its lighting position the neck and screw-threaded base of the bulb are disposed at a downwardly inclination. The body of the bulb is roughly rectangular in contour, as shown in Fig. 1, with a convexly curved upper wall Ill and side walls II and I! which diverge horizontally and are extended downwardly toward each other as shown in Fig. 8. The bulb has also end walls 13 and I4 converging downwardly and outwardly and meeting in smooth continuous curves at the end of the bulb and in its bottom.

The mount I5 extends into the bulb in concentric relation to the neck. A filament I6 is supported beyond the press of the mount in proper relation to the reflecting surfaces to be presently described. Any desired form of filament may be employed although I prefer a coiled coil filament of the type disclosed in the application of Charles Spaeth, Serial No. 15,605, since it is compact and of high intrinsic brilliancy and so may be located with greater optical accuracy than .a longer filament, and it also has long life under conditions of high operating temperatures.

As herein shown the bulb is provided with a reflecting disc, l1, located in its neck portion in position to reflect outwardly those rays which would otherwise be lost and also to act somewhat as a shield protecting the press of the mount from the intense heat developed in use. As herein shown the reflecting disc is perforated to receive insulating tubes which surround the leadin wires and to support the filament It.

It will be seen that the bulb above described is asymmetrical in shape. Its walls H and H are unequal in length and diverge unsymmetrlcally with respect to the axis of the mount IS. The upper wall It of the bulb is of continuous convex curvature whereas the bottom of the bulb is formed by walls of two distinct curvatures merging together. The end walls It and J4 are also dissimilar in character. All of the walls are preferably convex to withstand atmospheric pressure. A continuous reflecting coating of metallic silver is deposited upon the inside surface of the bulb in the proper location to define and reinforce the useful field of light. As herein shown the walls III, II and I2 are largely covered with the silvered reflecting coating, the edges of the coating in this case being terminated in a waterlevel line. In the bulb herein shown the curves of the walls and the silvered areas are so related that the light falling into the useful area will be substantially uniformly distributed and it will be understood that by suitably modifying the shape of the bulbs it is possible to illuminate the useful area, accordingly, to any desired or predetermined intensity gradient from brightest at the center of the illuminated area to dullest at the periphery or vice versa.

Figs. 5, 6, and 7 illustrate the bulb above described as located in position to illuminate with substantially uniform intensity the rectangular floor of a corner show window space and a limited part of the back and side walls of the show window space. The lamp further, is so designed and located that very little light shines through the window out into the street and into the eyes of observers looking into the show window. The lamp herein shown is located near the ceiling of the show window space and at the corner formed by the two windows. It causes a very high percentage of the total light emitted by the filament to fall within the useful area and with a predetermined distribution gradient characteristic. Such a result cannot be obtained by any symmetrical bulb regardless of the location of reflecting areas therein, but only by the use of elaborate external reflectors each calculated and designed to contribute its particular part to the total combined effect. The bulb herein shown represents a typical example of the present invention and has three different reflecting surfaces as may be seen by examining the trace of these surfaces formed by the intersecting planes,- perpendicular to the axis of the mount indicated by the line 8-8 in Fig. 2. Fig. 8 shows the line of intersection of these surfaces with the plane. It will be noted that there are three distinct and different curvatures in these surfaces each de-- signed to act in a different manner.

The outer dash lines in Figs. 5, 6 and 7 indicate in general the boundaries of the field of light emanating from the bulb and it will be understood that this is reinforced by reflected rays which would otherwise be lost to the useful field. Fig. 9 represents luminous intensity on a polar diagram in planes perpendicular to the floor of the show window space and passing from the filament of the lamp. The three planes chosen are represented by the lines A, B, and C in Fig. '7 and the corresponding intensity curves A, B and C in Fig. 9 indicate the intensity of the light coming from the filament which is assumed to be located at the point 0 in that figure. The distance from the point 0 to a given point on the closed curves A, B, and C, Fig. 9, is proportional to the light intensity at that point in the particular plane. It will be understood that the illustrated bulb is so shaped that much more light is reflected out along the plane 13, so as to reach the extreme corner of the. show window space, than is reflected along the plane C.

This characteristic of this particular reflecting bulb .will be better understood if its effect is considered when the bulb is suspended over a plane area to be illuminated and in such position that the axis of the neck of the bulb is perpendicular to this plane. It will be, noted from the drawings that the position of the bulb, when used for its specific purpose of lighting a store window, is at an angle to the floor of the store window-that is, the axis of the neck makes an angle of less than with the plane of the floor of the show window space. When the angle is 90 substantially a half cone of light leaves the reflecting bulb, the other half of the cone being in the shadow of the reflector. However this is not the important characteristic of this asymmetric reflecting bulb. Not only does substantially all of the light fall on one side of a line in the plane being illuminated through the point where the axis of the neck of the bulb cuts the plane but the distribution on the plane,--or half planeis unique. In the rough semi-circle of the lighted area on this plane, the greatest intensity of light is in the central portion, and the area at one side of this central area is more intensely illuminated than the area on the other Side, and both these side areas are illuminated at lower intensities than the central zone. This is an essential feature of this lamp which in the position shown in the drawings must force more light into those parts of the oblong window farthest from the lamp and less along the shorter side of the window, if substantially uniform illumination of the floor of the window is to be accomplished. Thus the intensity diagrams on three planes passing through the axis of the neck of the lamp perpendicular to the floor of the show window space, when the axis is perpendicular to the floor, said planes cutting the semicircle of light of the half cone at near the center and near the two edges would be'approximately the same as shown in the diagram Fig. 9, B representing the intensity at the center, C towards the short side of the window space, and A towards the long side.

Fig. 10 represents diagrammatically the illumination of the floor of the show window space along the lines D, E, and F of Fig. 7. It will be noted that the intensity of illumination over all parts of the floor is almost constant as shown by the curves D, E, and F in Fig. 10, the ordinates representing the intensity of illumination and the abscissae distance along the floor.

Attention is called to an important advantage incident to the asymmetrical reflecting bulb of my invention as compared to a separatelamp and external reflector in point of lighting efliciency and initial cost of installation. The best reflecting surface from the standpoint of emciency is a clean surface of metallic substance. In a reflector installed outside a lamp despite the best efforts to keep it clean, corrosive elements of the atmosphere furnish a gradual darkening and a loss of reflecting efliciency. Occasional polishing restores the efilciency for a time but eventually silver plated reflectors are worn out. A silver reflecting surface applied within the lamp however, is completely protected and its efliciency remains substantially constant throughout the life of the lamp. Further, the combination of outside reflector and lamp heretofore used compares unfavorably with the asymmetric reflecting lamp of my invention because the tungsten or free metal vaporized from the filament it is advisable to replace the bulb. In the case of my internally silvered asymmetric bulb, this deposit is generally of less importance since in most cases the reflecting area of the bulb includes the stem and tends to be cooler so that most of the timgsteniedepositedinthisarea.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp comprising a bulb approximately rectangular in contour and having side walls unsymmetrically diverging with respect to the major axis of the bulb and provided over a predetermined area with an inside silver coating constituting an asymmetrical reflector, and a filament located within the contour of the reflector.

2. An electric lamp comprising a bulb having. a neck and being asymmetricalin shape with respect to all possible planes passing through the axis of the neck of the bulb, having a metallic coating applied to a portion of its surface and terminating in a plane oblique to the axis of the neck, and a filament disposed in cooperative relation thereto.

3. An electric lamp comprising a bulb containinga light source and having a base, and a neck merging into side walls diverging unequally with respect to the axis of the neck and extending downwardly and inwardly to form the lower wall of the bulb, a rounded upper wall, and end walls, the upper wall and diverging side walls having a continuous reflecting coating terminating at its lower edge in a substantially horizontal plane when the lamp is located in a base-up illuminating position.

4. An electric lamp comprising a bulb containing a light source and having a base, and an elongated neck merging into diverging side walls which are inclined downwardly when the lamp is located in a base-up illuminating position and which are extended downwardly into a flat convex bottom wall which also has a general downward inclination, and end walls, and an upper wall of greater convexity than the lower wall, said upper wall and side walls having a reflecting coating limited at its lower edge to a substantially horizontal plane.

5 An electric lamp comprising a bulb containing a light source and having aneck and a body portion of irregular shape, a portion of the bulb being provided witha reflecting coating extending from the neck of the bulb toward the apex and bounded by a plane that makes an acute angle with the extended axis of the neck.

6. An electric lamp comprising a bulb containing a light source and having a base, a neck and a body portion provided with a reflecting coating which is disposed asymmetrically with respect to all planes passing through the axis of the neck of the bulb and bounded by a plane that makes an acute angle with the extended axis of the neck and being thus shaped to throw substantially more light upon one side of the illuminated area than upon the other.

CLARENCE BHtDSE-YE. 

